1. What is Bazett's Formula?

Bazett's formula is used to calculate the corrected QT interval (QTc) which accounts for heart rate variations. The QTc interval helps in assessing ventricular repolarization and detecting potential arrhythmia risks.

2. How Does the Calculator Work?

The calculator uses Bazett's formula:

Where:

• \( QT \) — Measured QT interval from start of Q wave to end of T wave (ms)
• \( RR \) — RR interval = 60 / HR (s)
• \( HR \) — Heart rate (bpm)

Explanation: The formula corrects the QT interval for heart rate, providing a standardized measure of ventricular repolarization.

3. Importance of QTc Calculation

Details: Accurate QTc calculation is crucial for diagnosing long QT syndrome, assessing arrhythmia risk, and monitoring drug effects on cardiac repolarization. A QTc >450 ms is generally considered prolonged.

4. Using the Calculator

Tips: Enter QT interval in milliseconds and heart rate in beats per minute. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal QTc value?
A: Normal QTc values are typically <450 ms for men and <460 ms for women. Values above these thresholds may indicate prolonged QT interval.

Q2: Why is QTc prolongation dangerous?
A: QTc prolongation increases the risk of life-threatening ventricular arrhythmias, particularly torsades de pointes.

Q3: When should QTc be measured?
A: QTc should be measured in patients taking medications that affect cardiac repolarization, those with syncope, or with family history of sudden cardiac death.

Q4: Are there limitations to Bazett's formula?
A: Bazett's formula may overcorrect at high heart rates and undercorrect at low heart rates. Other formulas like Fridericia's may be used in certain situations.

Q5: How is QT interval measured on ECG?
A: QT interval is measured from the beginning of the QRS complex to the end of the T wave, typically in lead II or V5.